During the production of many polymers, for example, polymers of conjugated dienes or copolymers of conjugated dienes and vinyl aromatic hydrocarbons, residual polymer tends to collect on the polymerization reactor walls and associated piping. This polymer is desirably removed for efficient subsequent use of the equipment. Removal of this polymer, however, can be difficult because the residual polymer is often gelled; i.e., it is highly crosslinked and can have a very high molecular weight.
Gelled polymer is conventionally removed by a process that includes steaming the reactor to remove hydrocarbons, employing water under increased pressure to physically fracture and break the polymer off of the equipment, draining the water and physically removing gelled polymer, and reconditioning the reactor. This process can take days to complete, and reactors may be out of service for up to two weeks during this process.
Molybdenum and tungsten metathesis catalysts have been used to depolymerize or fracture gelled polymers and thereby facilitate their removal from polymerization reactors. These catalyst compounds are employed in the presence of an olefin treating agent and a suitable solvent. Also, these catalysts are expensive and sensitive to air and moisture. When coupled with the fact that typical loadings include from 5 to about 100 parts catalyst per 100 parts polymer to be removed, these catalysts have not been technologically useful.
Thus, there exists a need in the art for a method of removing gelled polymer from polymerization reactor equipment.